1. Field
The present invention relates to a lithographic apparatus and a method for manufacturing a device.
2. Background
A lithographic apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. A lithographic apparatus can be used, for example, in the manufacture of flat panel displays, integrated circuits (ICs) and other devices involving fine structures. In a conventional apparatus, a patterning device, which can be referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of a flat panel display (or other device). This pattern can be transferred on (part of) the substrate (e.g., a glass plate), e.g., via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate.
Instead of a circuit pattern, the patterning means can be used to generate other patterns, for example a color filter pattern, or a matrix of dots. Instead of a mask, the patterning device can comprise a patterning array that comprises an array of individually controllable elements. An advantage of such a system compared to a mask-based system is that the pattern can be changed more quickly and for less cost.
A flat panel display substrate can be rectangular in shape. Lithographic apparatus designed to expose a substrate of this type can provide an exposure region that covers a full width of the rectangular substrate, or that covers a portion of the width (for example half of the width). The substrate can be scanned underneath the exposure region, while the mask or reticle is synchronously scanned through the projection beam. In this way, the pattern is transferred to the substrate. If the exposure region covers the full width of the substrate then exposure can be completed with a single scan. If the exposure region covers, for example, half of the width of the substrate, then the substrate can be moved transversely after the first scan, and a further scan is typically performed to expose the remainder of the substrate.
For loading and/or unloading a substrate on the substrate table on which the substrate is supported during exposure of a pattern on the substrate, the known lithographic apparatus comprises a substrate handler. A substrate handler for a lithographic apparatus comprises a robot which places the substrate on the substrate table. As it is undesirable to contact the substrate at the upper side, the substrate table is provided with lifting pins that can be moved in and out of the substrate table in a substantial vertical direction. In a retracted position the pins are retracted in the substrate table so that the substrate can rest on a support surface of the substrate table. In a lifted position of the lifting pins a substrate can be held in an exchange position, in which the forks or other holding elements of a robot can be placed under the bottom side of the substrate, so that the substrate can be taken over by the robot, or vice versa, without contacting the top side of the substrate.
In this known substrate handler separate lifting means have to be provided in the substrate table in order to make exchange of a substrate possible. It is undesirable to have a loading/unloading mechanism on the substrate table, since such additional means on the substrate table can have a negative influence on the final product quality. Furthermore, the use of lifting means requires a considerable amount of space above the substrate table, which space is required for other components of the lithographic apparatus, such as in particular a lens column.
Therefore, what is needed is a system and method that provide a substrate handler for loading and/or unloading a substantially flat substrate on/from a substrate table, where the substrate table comprises relative small adaptations for the loading and unloading of substrates. Another aspect of the invention is to provide a substrate handler that requires a relatively small space above the substrate table to load and/or unload a substrate on/from substrate table.